Critical dimensions of memory devices in semiconductor devices are ever shrinking. And three-dimensional (3D) memory devices are one way designers have achieved greater storage capacity while making dimensions small, but to increase efficiency of such memory devices even smaller critical dimensions of oxide/poly multilayer lines as bit lines of 3D memory are desired.
Current techniques for forming multilayer lines of 3D memory typically use photo resist to form a desired pattern in an advanced patterning film (APF) layer, which is then used to etch polysilicon and oxide layers formed beneath the APF layer on a device substrate. The desired pattern in the APF layer typically includes spaced apart regions of APF material, and the regions of APF material are then used to pattern the multilayer lines. Thus, the dimensions of the current multilayer lines of 3D memory are defined by the dimensions of the spaced apart regions of the patterned APF layer, decreasing the width of the spaced apart regions of the APF material will allow for a smaller critical dimensioned multilayer lines of 3D memory.
3D memory multilayered lines typically comprise a plurality of alternating silicon oxide and poly-silicon layers. Each layer has a thickness of approximately 5000 Å. Typically, an advanced patterning film (APF) of approximately 6000 Å may be used to resist etching chemicals when etching the multilayered silicon oxide and poly-silicon layers. But the advanced patterning film (APF) layer is typically made of amorphous carbon, which is a relatively soft material. And this material is susceptible to falling apart or deteriorating when its aspect ratio is too large (e.g., aspect ratio>7). Besides, a thin patterned APF will suffer corner damage. Problems with the APF could compromise the later processing or etching of the multilayer lines of 3D memory. Accordingly, there are limits to how small the spaced apart regions of the APF layer may be, and so there are also limits as to how small the critical dimensions of the multilayer lines of 3D memory formed using a patterned APF layer approach may be.
Thus, it is desirable to find a new approach for decreasing the critical dimension of multilayer lines of 3D memory.